Analysis of Equipment Failures as a Contributor to Hydrogen Refuelling Stations Incidents

Abstract

Hydrogen is a sustainable, clean source of energy and a viable alternative to carbon-based fossil fuels. To support the transport sector’s transition from fossil fuels to hydrogen, a hydrogen refuelling station network is being developed to refuel hydrogen-powered vehicles. However, hydrogen’s inherent properties present a significant safety challenge, and there have been several hydrogen incidents noted, with severe impacts to people and assets reported from operational hydrogen refuelling stations worldwide. This paper presents the outcome of an analysis of hydrogen incidents that occurred at hydrogen refuelling stations. For this purpose, the HIAD 2.1 and H2tool.org databases were used for the collection of hydrogen incidents. Forty-five incidents were reviewed and analysed to determine the frequent equipment failures in the hydrogen refuelling stations and the underlying causes. This study adopted a mixed research approach for the analysis of the incidents in the hydrogen refuelling stations. The analysis reveals that storage tank failures accounted for 40% of total reported incidents, hydrogen dispenser failures accounted for 33%, compressors accounted for 11%, valves accounted for 9%, and pipeline failures accounted for 7%. To enable the safe operation of hydrogen refuelling stations, hazards must be understood, effective barriers implemented, and learning from past incidents incorporated into safety protocols to prevent future incidents.

1. Introduction

The increasing acceptance of hydrogen as an alternative to conventional carbon-based fuels has resulted in the increasing widespread adoption of hydrogen refuelling stations worldwide. The introduction of hydrogen-powered vehicles necessitates the development of hydrogen refuelling station (HRS) networks. The safe operation of HRS is paramount; therefore, effective safety measures must be implemented to ensure safe operations and successful development [1,2]. Hydrogen remains a main contender to replace carbon-based fuels. This is due to its inherent properties; when hydrogen is combusted, no greenhouse gas is emitted, thus making hydrogen an environmentally friendly option [3].

However, the inherent properties of hydrogen present a safety challenge in the safe and sustainable operation of hydrogen refuelling stations. The main safety challenge associated with HRS is that it is highly flammable, the lightest chemical element, odourless, and colourless (making it difficult to detect when released), and the storage tanks are operated at elevated pressures and cryogenic temperatures. Across the world, the adoption of hydrogen refuelling station technology remains slower than expected. Figure 1 presents an overview of the distribution of operational HRS worldwide by the end of 2024. There is a total of 1160 hydrogen refuelling stations (HRSs) operational worldwide, with 64% of operational HRS in ASIA, predominantly in China, South Korea, and Japan, followed by Europe with 25%, mainly in Germany, other continents with 3%, and 8% in the United States of America [4]. There is an increasing construction and commissioning of hydrogen refuelling stations worldwide, as governments are decarbonising the transport sector [5].

Based on the available data, there are no operational hydrogen refuelling stations on the African continent. It remains important that all governments commit to the transition from carbon-based fuels to hydrogen fuels in pursuit of reducing greenhouse gas emissions in the atmosphere and ultimately reducing climate change.

There has been an increasing number of hydrogen incidents reported at different stages of hydrogen refuelling stations, and these incidents have had a catastrophic impact on people and assets [6,7], thus creating a negative public perception of the transition from a carbon-based to a hydrogen energy system. In-depth analysis of hydrogen incidents in the hydrogen refuelling station value chains can provide insights into common equipment failures and their related causes. The identified insights can be used to enhance safety protocols in the HRS to prevent or mitigate future incidents. Nouman Rafique Mirza et al. [7], in an analysis of 32 hydrogen incidents in the process industry, suggest that the majority of the incidents were fire (43.7%), explosion (31.3%), both fire and explosion (15.6%), and the balance are near misses, and these incidents were mainly due to human error and design errors. Rami Alfasfos et al. [8], in an analysis of 82 hydrogen incidents since year 2000, concluded that a significant number of incidents occur during distribution (40%), storage (24%), end use (hydrogen dispensers) (16%), compressors (11%), and electrolysers (9%), with inadequate maintenance operations and deviation from procedures being the key contributors to these incidents. Junji Sakamoto et al. [9], in an analysis of the United States of America (USA) and Japan, identified 43 hydrogen incidents that occurred in the HRS, revealing that flange leaks, valves, seals, and weld joints were the main equipment failures, predominantly due to design errors. All the above studies provide pertinent insights into hydrogen incidents to be incorporated into HRS safety protocols.

However, with these different insights, it is significant to further analyse the hydrogen incidents at different stages of the hydrogen refuelling stations. In this study, incidents that occurred in the hydrogen refuelling station value chain were considered, including storage tanks (associated components, pumps, compressors, valves, and pipelines) and the dispensing system. The incidents during hydrogen distribution to the HRS value chain are excluded from this study.

This study aims to analyse incidents in the hydrogen refuelling station value chain, including storage and dispensing systems, with the objectives of determining key equipment failures and their causes. This study analysed the hydrogen incidents stored in the HIAD 2.1 and H2tool.org databases. The two databases have been specifically developed for the storage of hydrogen incidents that have occurred worldwide, enabling the sharing of learnings among hydrogen technology users. This study aims to provide insights from previous hydrogen value chain incidents, which can be extrapolated to HRS, with the goal of preventing future incidents. The study body of knowledge contributions:

• This study provides a thorough analysis of key contributors to incidents at hydrogen refuelling stations, with a particular focus on the frequent equipment failures and the underlying causes of these failures.

2. Materials and Methods

In this study, a mixed research approach was employed to analyse previous hydrogen incidents that occurred within the HRS value chain, as documented in the hydrogen incident database. The HIAD 2.1 and H2tool.org databases were used for data collection, as they are dedicated to storing hydrogen incidents. Table 1 presents the number of incidents obtained from different databases. The study sample size consists of forty-five incidents that occurred in hydrogen refuelling stations’ value chains; excluded from this study are incidents that occurred during hydrogen transportation to HRS. The analysed incident occurred between 1990 and 2024. For data selection and filtering, the following steps were followed:

(a)

HIAD database, incident filtering by application type (hydrogen refuelling stations), H2tool.org filtered by application type (fuelling stations).

(b)

Review of the incident, full description to gain an understanding of what happened, and the failed equipment.

(c)

Review the causes and consequences of the incident.

Table 1. Database of hydrogen refuelling incidents.

Database Name	Number of Incidents Reported (HRS)	Database Administrator
HIAD	716(28) Accessed 20 April 2025	European Commission Joint Research Center, Petten, Netherland
H2tool.org	67(12)	Hydrogen Safety Panel
Online	5

Table 1. Database of hydrogen refuelling incidents.

Database Name	Number of Incidents Reported (HRS)	Database Administrator
HIAD	716(28) Accessed 20 April 2025	European Commission Joint Research Center, Petten, Netherland
H2tool.org	67(12)	Hydrogen Safety Panel
Online	5

Thus, this study’s objective is to ascertain the frequent equipment failures in the hydrogen refuelling station value chain, the root causes of the equipment failures, and to enable extrapolation of insights to be considered when developing the HRS.

3. Results

This study thoroughly reviewed incidents that occurred in the hydrogen refuelling value chain, and the incident data used were collected from the HIADA 2.1 and H2tool.org databases, as well as online sources, as indicated in Table 1.

Table 2. Process/equipment failures consequences (injuries and fatality rates).

Process Equipment	Injured (Rate)	Fatality (Rate)
Compressor (5)	0	0
Dispenser (15)	0	0
Pipelines (3)	0	0
Storage Tanks (18)	12 (67%)	3(17%)
Valves (4)	0	0
Total (45)	27%	7%

provides an overview of the number of incidents in the different process equipment within the HRS value chain, as well as the injury and fatality rates associated with each type of process equipment. The analysis indicates that only storage tank incidents resulted in injuries and fatalities to people in the vicinity when the incident occurred. The injury rate was 27%, while the fatality rate stands at 7%. These incidents were primarily caused by the loss of containment of hydrogen from storage tanks, leading to fires, explosions, and subsequently resulting in injuries and fatalities. As the adoption of HRS continues, it is important to understand the risks associated with HRS and implement effective safety measures to prevent incidents or mitigate against the impacts of the incident.

Table 3. Incident geographical distribution.

Incident Regions	Numbers	Process Equipment
Asia	5	Storage (3); dispenser (2)
Europe	19	Dispenser (5); storage (2); other (11)
North America	8	Storage (7); dispenser (1)

presents the geographical distribution of incidents; the distribution statistics exclude the 12 incidents obtained from the H2tool.org database. The data indicates that the majority of incidents reported occurred in the European continent (mainly in France, the United Kingdom, Sweden, and Germany), followed by North America, and lastly, Asia (South Korea and Japan), and most of these incidents in the United States occurred in the storage tanks. Based on the geographical number of operational HRS presented in Figure 1, Asian countries have a significant number of operational HRS, but with fewer incidents reported and available in the public domain. However, it must be noted that incident reporting and investigation play an important role in the prevention of future incidents. It is important to share learnings with different users to ensure that these learnings are shared and embedded worldwide.

According to Rialivhuwa Nekhwevha et al. [6,10], a Standard Operating Procedure (SOP) is a detailed written instruction that guides how a specific task must be performed, which ensures uniformity in how activities are performed. The SOP must cover different modes of operation, i.e., normal operation, abnormal operation, temporary operation, and emergency operations, and the operators must be trained and declared competent in the activities they are performing. Figure 2 presents the mode of operation when the incident occurred, and a significant (89%) incident occurred during normal operation (i.e., normal refuelling, pumping of liquid and compressions, etc.), and this is attributed mostly to equipment failures during operation, and followed by temporary operations (9%), including testing, during maintenance activities accounted for 2%.

According to the Centre for Chemical Process Safety (CCPS), normal operation refers to the continued process operation that supports operation within safer operating limits between the start-up and shutdown of the process equipment [10].

From the forty-five incidents analysed, during normal operation modes, incidents occur due to sudden and unexpected equipment failures, resulting in a loss of hydrogen containment from the primary containment to the atmosphere. The process equipment must be operated within agreed-upon parameters and maintained according to established maintenance strategies to prevent sudden process equipment failures.

Hydrogen is the lightest chemical element, highly flammable [11,12], and when released from primary containment, it easily ignites. However, Figure 3 presents a consequence of hydrogen release from primary containment in the value chain. This study reveals that in 62% of the evaluated incidents, the released hydrogen did not ignite, while 27% of hydrogen releases resulted in explosions at the hydrogen refuelling stations, and 11% led to fires. Further analysis reveals that in all incidents that occurred in the dispenser process equipment, the hydrogen released did not ignite, as noted by Astbury. G.R. et al. [13] stated that hydrogen release from primary containment does not mean it will auto-ignite; a proper hydrogen–air mixture and a source of ignition are required.

This study also reveals that most fires and explosion incidents occurred in storage tanks, and most of these incidents were due to bursting disk/rupture disk or pressure control system failure. When this system fails, a large quantity of hydrogen is released into the atmosphere, creating a hydrogen-to-air mixture that easily ignites [14].

For the explosion incidents, this study reveals that 67% of these incidents were a result of hydrogen release from the storage tank, 17% of the incidents were a result of release from the valves, 8% of the incidents were a result of release from the compressor, and 8% from the pipelines. Fire and explosions are often associated with catastrophic impacts to people and equipment in the vicinity of the incidents.

Figure 4 presents the frequent equipment failures in the hydrogen refuelling stations value chain worldwide. In this section, two research findings are highlighted: (1) the frequent equipment failures in the hydrogen refuelling stations value chain; and (2) key contributors to frequent equipment failures in the HRS value chain.

First, this study reveals that hydrogen storage tanks experienced a higher incident frequency, and these incidents resulted in equipment damage, injuries, and fatalities. In total, 40% of the reported incidents occurred in the storage tanks. This study further reveals that the prevalent failures are associated with the pressure control system, i.e., bursting disks, rupture disks, welds, and pressure safety valves. Thus, failures were mostly associated with deviation from operating procedures and design deficiency of the pressure control system components. The component selected must be compatible with hydrogen, as hydrogen normally attacks most materials of construction due to its inherent properties. The ASME B31.12 code outlines the wide-ranging requirements that must be adhered to when selecting equipment for use in the hydrogen value chain.

The hydrogen system is often associated with the embrittlement phenomenon. When materials are exposed to hydrogen, hydrogen diffuses into the material, which affects the material’s mechanical properties, resulting in sub-critical crack formation [15]. ASTMF2078-22 provides insights into acceptance criteria for hydrogen embrittlement testing. There are several ways to prevent or mitigate against hydrogen embrittlement:

• Controlling material hardness and conducting post-weld heat treatment to reduce the hardness and temper material residual stress.
• Use dry, low-hydrogen electrodes (such as E7018-1) and pre-heating techniques for welding.
• An elevated temperature bake-out at a minimum temperature of more than 205 °C is necessary to drive out hydrogen if it diffuses into the metal during the welding or operating process.
• To stop hydrogen surface reactions, apply a weld overlay, cladding, or protective linings.
• Heavy-wall equipment handling hot hydrogen shutdown and start-up procedures must be adequately controlled to enable the pressurisation sequences as a function of temperature.
• Hardness tests and post-weld heat treatment (PWHT) are critical in the material manufacturing process, and they must not be ignored

The hydrogen dispenser failure is the second most frequent equipment failure, and accounts for 33% of the reported incidents. The frequently failing components in the dispenser system include flexible hoses, valves, and nozzles. In all the incidents that occurred in the dispenser HRS value chain, the released hydrogen did not ignite; however, it dispersed quickly into the atmosphere, and no serious consequences were recorded in this HRS value chain. The third contributor is compressor failure, accounting for 11%, with most incidents occurring around the compressors. Additionally, 9% of incidents are due to valve failures, and 7% are due to pipeline failures. The number of incidents in the public domain remains low; this can be attributed to intellectual property or incidents’ legal implications, thus preventing incident information sharing.

The selection of material that is not susceptible to hydrogen embrittlement is critical in a hydrogen environment [11].

Table 4. Incident sub-equipment failure and causes.

Main Equipment Failure	Number of Incidents Reported (HRS)	Database Administrator
Hydrogen storage tanks (18)	Bursting disc (2) Pressure safety valve (1) Rupture disc (2) Fitting connections (1) Flange bolts (1) Plugs (2) Pressure control system (1) Welds (2) Other (5)	Procedure (human error)—38% Design deficiency (material incompatibility, manufacturing defects)—29% Inadequate management of changes—5% Poor maintenance—10% Compressor vibration—5% Stress corrosion—5% Incorrect installations—10%
Hydrogen dispenser (15)	Hose (7) Breakaway coupling (1) Nozzles (1) Valves (2) Other (4)	Design deficiency Poor maintenance
Valves (4)	Valves packings	Inadequate maintenance
Compressor (5)	Crankshaft bearings Pressure switches Seals and filters	Vibrations Weld failures System logic failures
Pipelines (2)	Pipelines	Embattlement

presents the sub-equipment that failed and the causes of the equipment failures. In the liquid hydrogen refuelling stations, cryogenic storage tanks are used; furthermore, these tanks are vacuum-insulated to prevent excessive liquid evaporation due to heat leakage. The storage tanks are designed for specific pressure and temperature as per the codes, including ASME boiler and pressure vessel codes, API 620, and CGA H-3, which is the standard for cryogenic tanks and must be considered when designing the tanks. The HRS value chains must be subjected to risk analysis (different methodologies can be used, i.e., HAZOP studies and Failure Mode Equipment Analysis (FMEA) to determine the possible hazards associated with the HRS value chain, and the layer of protection that must be implemented to prevent or mitigate against over-pressurisation scenarios.

Overall, the storage tank incidents were a result of procedure deviation or human error, which accounted for 38% of the total number of incidents in the storage tanks. In most cases, the storage tank vacuum failed, resulting in excessive evaporation, leading to high storage tank pressure.

The design deficiency accounted for 29% of the total incidents; the hydrogen-incompatible material used in storage tank components ultimately failed due to the hydrogen embrittlement phenomenon. Incorrect installation of the equipment and poor storage maintenance contributed 10% each. All operating equipment must have a maintenance strategy developed, and it must be executed according to plan to ensure equipment functionality and reliability at all times, which potentially prevents equipment failures [16], and people performing maintenance activities must be trained and declared competent in executing the maintenance activities. In total, 33% of the reported incidents were due to dispenser failures, and 46% of the hydrogen dispenser failures were associated with hose failures during utilisation, leading to loss of containment of hydrogen.

The common cause of dispenser failures is due to design deficiencies in the hose and inadequate preventive maintenance of the hoses; it is important that maintenance is performed according to the requirements. Valve failures accounted for 9% of the total incidents, and the valve failures were due to inadequate maintenance of the equipment. The compressor failures accounted for 11% of the incidents, and the common component failures were crankshaft bearings, pressure switches, seals, and filters. The process pipeline failures accounted for 7% of the incidents.

4. Conclusions

This study reviewed incidents in the hydrogen value chain. The reviewed incidents were collected from HIADA 2.1 and H2tool.org databases. This enabled the identification of frequent equipment failures and the causes of the failures in the hydrogen refuelling stations’ value chain. Thus, the highest risk in the hydrogen value chain is in the storage tanks. This study reveals that the incident frequency and severity in the HRS value chain are more frequent in storage tanks and account for 40% of the total incidents analysed, with a 27% injury rate and a 7% fatality rate reported. In the other sections of the HRS values chain in scope, there were no fatalities or injuries reported as a result of the incidents. These incidents occurred frequently during normal operation of the storage tanks, with hydrogen storage tank components failing due to hydrogen embrittlement and storage tank over-pressurisation due to deviations from the procedure. During the design phase of the project, applicable standards and codes are adhered to, which will ensure that the selected construction materials are compatible with hydrogen.

Process equipment cannot be operated indefinitely; equipment must be maintained to ensure that it continues to function as designed and within acceptable limits. This will maintain optimal performance and longevity of the equipment. The storage tank risks must be identified, and over-pressurisation scenarios must be thoroughly evaluated to ensure that over-pressurisation barriers are effective, appropriate, and maintained as per the agreed frequency. The standard operating procedures must be accurate, clear, and concise, and the system user must be trained on the procedures and declared competent. These insights can play a crucial role in ensuring the safe deployment and operation of hydrogen refuelling station networks worldwide, which are vital for the transition from carbon-based fuels to a hydrogen economy.